The human antenatal and neonatal growth revisited Oreste Battisti MD, PhD, Academic Professor of Pediatrics, Faculty of Medicine, University of Liège (Belgium), Department of Pediatrics and neonatal medicine. Route de l’hôpital, Bat 35 4000 LIEGE (B) Oreste.battisti@ulg.ac.be Abstract We made firstly an analysis of several published charts concerning the human antenatal and postnatal growth. We made an analysis of the absolute and of the velocity changes in body weight, in length and head circumference. The fetal curves have a diagnostic purpose on the normality of growth during the fetal life. They are derived from measurements done either in utero or at birth and are validated from 25 to 42 weeks. From these diagnostic charts, the best on a mathematical and statistical point of view is that by “Dombrowski”. Several other fetal curves can be criticized for not meeting all the criteria of a statistical normal population, mainly concerning the body weight. The combined (fetal and postnatal) charts are constructed from measurements done at birth and longitudinally afterwards: they are validated from 25 to 60 weeks. The clinicians having in care fragile neonates (those born before 30 weeks or below 1000g or those combining a prematurity and a fetal growth restriction) have the important task which is to give the best nutrition for these neonates and, by the way, to see if the actual growth is optimal. This can be done by measuring longitudinally the three parameters of growth and by plotting the results on a combined chart. The postnatal growth of a premature baby can hence adequately be followed for they take into account the interruption of fetal life, the necessary adaptation after birth and the consequent priorities of growth in organs. Among the combined charts, the “Gairdner” and “Battisti” meet the criteria of a normal population for all parameters of growth. We made secondly the analysis of velocity observed in the different parameters of growth (d BW, d BL, d HC) from 25 to 60 weeks of age. The analysis concerned their absolute values and their ratios. The gain in BW over the gain in HC ratio is strongly correlated to the age of the newborn. It can be used from 25 to 60 weeks of age: d BW g / d HC cm = 44 PCA – 1138 (r = 0.973, p < 0.00001). This second way to appreciate the adequacy of growth is interesting for length in a the fragile neonates is not always easy to measure. Key words: fetal growth, prematurity, nutrition, postnatal growth. INTRODUCTION Growth in general, and even more when it concerns a fragile neonate or child, is an important and constant aspect of care for the family and for the medical staff (1-9). Growth is made of different dimensions, not having the same priority at a given time (116). A compromised growth during special periods can be associated or followed by an abnormal development (4, 12-35). The most frequently used parameters for assessing growth are: - the body weight (BW) and length (BL), the circumferences of head (HC) and (left) arm, the skin folds; these represent the absolute indices; - beside these we can use the relative indices such as the ponderal index, the body mass or Quetelet’s index: they are the ratios among different parameters. These indices have the purpose to assess the harmony of growth. - finally, one can also calculate the velocity indices who have the purpose to assess the variability over a period of time of a given parameter, and hence possibly to appreciate the influence of nutritional and or endocrine factors. The present work makes the analysis of the different growth charts concerning the fetal, neonatal and post neonatal periods. It aims to bring to the clinician pragmatic criteria to appreciate the adequacy of nutrition and the longitudinal growth of the most fragile newborns: those born before 30 weeks, those having a body weight below 1001g, those combining a prematurity and retarded intrauterine growth. Concerning these populations, the simple questions « which curve, what parameters of growth should be chosen? » might become complex (12- 35b). POPULATION, METHODS AND STATISTICS The types of charts (18, 27-52). 1. In the fetal charts, the measurements are done by the obstetricians during intrauterine life by ultrasounds (1, 2, 3, 7, 46-52). 2. In the diagnostic charts, the measurements are done as soon as possible at birth in babies born at different gestational ages, these being gathered in progression of gestational age classes: the « Lubchenco », « Usher-Mclean », « Babson » and « Dombrowski » charts are some examples of these. 3. In the combined charts, the populations include the babies measured at birth and in their postnatal life till 60 weeks: the « Dunn », « Gairdner », « Cope », « Battisti » charts are representative of these. In these, growth is evaluated in a longitudinal way. It does also exists charts for singletons, for twins and triplets, for babies with a starting body weight < 1000g or a gestational age < 30 weeks. All the vectors of growth are found in “Babson”, “Battisti”, “Dombrowski”, “Gairdner”, “Lubchenco” and “Usher-Mclean” works (10, 19, 27, 32, 40, 46, 47). For that reason, these charts have been analysed in details in the present work. The items that were considererd: We examined the statistical normality of the population, the body weight and length, the head circumference, the arm circumference. We analysed the absolute weekly gains of these parameters and also the weight over length and weight over head circumference ratios. The statistical calculation: We estimated the correlations between these different indices of growth with gestational age, searching simple and multiple regression coefficients and of variations coefficients. We also determined the median, mean and mode values for the data to ensure that the sample volume of population follows the criteria of normality (53, 54). RESULTS 1.Concerning the analysis of normality in populations presented in the different charts . All the described charts have a sufficient sample to reach the statistical significance. A population can be considered normal from a statistical point of view if median = mean = mode. Moreover, the coefficient of variation of a given parameter has to be comprised between 4 and 18 %. We can find the results in Table I. The coefficients of variation (CV in %) is the ratio of the standard deviation over the mean times 100. The CV is calculated for the body weight (BW), the length (BL) and the head circumference (HC). As far as BW is concerned, one can see that normality of population is not encountered for the charts « Lubchenco » and « Usher-Mclean ». The other parameters are in the range of normality. Table I .Analysis of the coefficients of variation ( CV ) for the 3 parameters of growth : for body weight ( BW ), for length ( BL ) and for head circumference (HC). (*) means outside the range of a normal population. Author, year(s) Intervals in weeks , parameters CV : BW CV : BL CV : HC Babson, 1970,1976 26-42 ; 26-92 ; BW,BL,HC 14 8 9 Battisti, 1992 25-60 ; BW,BL,HC,PI 13 7 6 Dombrowski 1992, 26-42 ; BW,BL,HC 13 5.3 4 Gairdner 1971 26-60 ; BW,BL,HC 17 4.4 4 Lubchenco 1966, 1970 26-42 ; BW,BL,HC, PI 22 (*) 11 10 Usher-McLean 1969 25-44 ; BW,BL,HC 26 (*) 8 6 Among the diagnostic charts, the most normal from a statistical point of view is « Dombrowski ». Among the combined charts, both are equivalent for the 3 considered parameters, and the values respond to the statistical requests for a normal population. 2. About the analysis of the correlations between the different parameters of growth and the gestational age. The original data can be found in the respective references. Table II. The Mathematical correlations between parameters of growth and gestational age. Author PCA and BW PCA and BL PCA and HC Babson * BW= 176 PCA – 3696, BL = 0.8 PCA + 17.5, HC= 0.48 PCA + 14, SD = 2401 ; r = . 99 SD = 10.8 ; r = . 99 SD = 6.63 ; r =. 98 Battisti * =174 APC – 3665, SD = 434 ; r = .99 Dombrowski * = 174 APC – 3732, SD = 1262; r=.99 Gairdner * = 206 APC – 5051, SD = 2672; r = . 98 Lubchenco * = 163 APC – 3375, SD = 1303; r =. 99 Usher-McLean * = 177 APC – 3741, SD = 1350; r =. 99 = 0.9 APC + 11.5, SD = 4; r= . 99 = 1.06 APC + 6.64, SD = 7.8; r=. 99 = 0.89 APC +13.6, SD = 13; r =. 99 = 1.25 APC + 2.5, SD = 7.1; r =. 99 T= 1.11 APC +7, SD = 8.35; r =. 99 = 0.6 APC + 9.72, SD = 2.4 ; r= . 98 = 0.721 APC + 5.3, SD = 5.3; r = . 98 = 0.5 APC + 13.94, SD = 6.5; r = . 98 = 0.58 APC + 10.5, DS = 4.8; r =. 97 = 0.81 APC + 3.1, SD = 6.2; r=.99 The mathematical analysis of data in different curves gives the possibility to build up the formulas with the coefficient of correlation (r) and of determination (r2) concerning each parameter of growth and the gestational age (53, 54). The values of “r” (0.98 à 0.99), reflect a high associative force between the parameters and the age of infants. Moreover, these associations show a very good reliability: SD is comprised between 6 and 8 %. The following formulas resume the associative relationships and may be use in either direction (PCA means post conceptional age): - Weight in g = 175 PCA weeks – 3665 ( SD = 13 % ) - Length in cm = - HC in cm PCA weeks + 11 = 0.6 PCA weeks + 10 ( SD = 8 %) ( SD = 6 % ) As an example, a baby of 30 weeks has a predicted weight of 1585 g, a length of 41 cm and a HC of 28. On the other side, a weight of 5000 g correspond to a PCA of 49.5 weeks, a length of 35 com to a PCA of 24 weeks, and a HC of 35 com to a PCA of 41.7 weeks. 3. About the analysis of the weekly increments in growth for the 3 parameters during the different periods of post conceptional age. The different curves are examined one by one during the different sliced periods of life. Each parameter of growth, in the absolute and relative value, is considered from the increments observed in the corresponding periods. We calculated the correlations between the following ratios through all the sliced periods of age going from 25 to 60 weeks, both in the diagnostic and in the combined curves. The significant correlations between ages and considered ratio are the following ones: - [ d W g / d HC cm ] per week = 44 PCA – 1138, SD = 13 %, r = 0.973 ; - [ d L cm / d HC cm ] per week = 0.094 PCA – 1.543, SD 14 %, r = 0.88 ; As an example, for a baby of 28 weeks, the ratio “d W g/d HC cm” is expected to be 94, and the ration “ dL cm / d HC cm” is expected to be 1.09 meaning an harmonious growth of body. Table III. The Analysis of velocities (weekly increments) for BW, BL and HC, and also the relative indices of them ( data with their mean and 95 % confidence intervals values). Sliced d BW g d BL cm d HC cm dBW/dBL dBW/dHC dBL/dHC 115 1 1.1 115 110 0.9 (70- 160) (.85-1.15) (0.9 -1 .2) (35-115) (100-133) (0.95-1) 145 1.13 0.9 125 164 1.34 (100- 190) (0.63-1.63) (0.7 – 1.3) (90-160) (115-213) (0.44-2.24) 170 1.2 0.7 182 242 1.35 (108-232) (.94– 1.54) (0.7-1.3) (86-288) (117-376) (0.9-1.79) 208 1.23 0.8 178 253 1.56 (148-268) (.94- 1.54) (0.65-0.95) (70-286) (153-353) ( 0.97-2.15) 242 1 0.7 272 392 1.5 (167-317) (0.6 – 1.4) (0.15-0.9) (174-370) (184-600) (1.1-2.5) 213 0.8 0.5 273 459 1.8 (129 – 297) ( 0.3– 1.3) (0.2-0.8) (166-380) (87-731) (1.1-2.5) 143 0.7 0.33 310 621 2.4 (43-243) ( 0.1– 1.3) (0.13-0.53) (0- 645) (0-1321) (0.5-0.34) 70 0.25 0.17 280 420 1.47 (0 – 168) (0 – 0.6) (0 – 0.48) (0 – 583) (0 – 400) (0- 1.25) 170 0.9 0.6 223 355 1.66 (57 – 283) (.15 – 1.65) (0.04-1.1) (82-366) (14-686) ( 0.88– 2.44) Periods expressed in weeks 26-28 28-30 30-32 32-34 34-36 36-38 38-40 40-42 Mean Conclusions concerning the analysis of the absolute values in diagnostic curves: - For the weight, the weekly gains are highest during the 34-36 sliced period ; - For the length, this highest weekly gain is observed in the 32-34 sliced period ; - For the head circumference, this is observed in the 28-30 weeks period. Conclusions concerning the analysis of the relative values in diagnostic curves: One can observe that the highest values are found at the end of pregnancy. The disparity of the ratio “body growth over head growth” is obvious after 34 weeks, and the ratio of body weight over length is obvious after 36 weeks. DISCUSSION The normal growth has always been important for the clinician. A « normal » growth is defined by the presence of parameters being comprised in normal values and presenting a sort of harmony between them. Normality is however differently defined among the existing charts: either the mean and standard deviations, or the percentiles, or the mean and confidence intervals. A growth is considered to be abnormal if the parameters are insufficient or excessive in their absolute values, also if their velocities are outside the normal range. The body weight is the easiest parameter to obtain. It is supposed to resume all dimensions of growth (4, 8, 11). What the BW is concerned, the charts « Lubchenco » and « Usher-Mclean » are questionable in order to appreciate the normality of that parameter, as the CV is largely outside the range. The chart « Dunn » is a combined type and has a value till 60 weeks only for the BW. The charts « Babson » and « Dombrowski » are diagnostic and meet all the criteria of a normal population: they should be used only at birth to appreciate the preceding fetal growth. The diagnostic charts do not offer the predictive correction due to noticeable changes observed after birth. In case of prematurity, the fetal growth is interrupted, a period of adaptation cannot be avoided, and one can observe changes in the priorities of growth among organs (4, 6, 7). During the fetal period of growth, the placenta intervenes in great part. The increasing influence of insulin during the fetal life and the later progressive “placental fatigue” explain the shape of different diagnostic curves (2-4, 8, 12-14,68). After birth, the endocrine and metabolic mechanisms present in neonate have to continue without the help of placenta but hopefully with an appropriate nutrition. These aspects normally allow the baby to reach a good growth in the different parameters (4, 6, 7, 9). In fact, beside body weight, other parameter such as the head circumference, are also important, especially in neonatal medicine. The HC is correlated to cerebral mass which represent a large part of metabolism and requirements in calories and proteins. This is obvious in the previously defined fragile babies. The most fragile babies being those born with a birth weight below 1000g or below 30 weeks, and those combining a prematurity and growth retardation (2,3,4,5,8,9,14). Particularly in these babies, it would be better to use charts meeting the criteria of a normal population to assess the global growth. The « Babson », « Dombrowski », « Gairdner » and « Battisti » charts meet the statistical criteria of normality concerning the 3 parameters. We can mention that for the first 2 weeks following birth only, the charts « Dancis » and « Gross » are useful for following the postnatal progress of respectively the BW and the HC. A normal growth is associated with a reduction of the mortality and morbidity that can be observed after a prematurity and an abnormal fetal and postnatal growth. The importance of nutrition in its quality, quantity an rapidity for an optimal long term development have extensively been studied ( 3,4,5,8,10,13,15,16,17,18-26,46,51,55-68 ). The combined charts take into account these facts. As it is not always easy to get all the parameters, in order to appreciate correctly the harmony of growth, one may use two parameters of growth (BW and HC) combined in a ratio according to a mathematical formula: dBW in g / d HC cm = 44 PCA weeks – 1138 ( SD = 13 %, r = 0.973, p < 0.0001 On a clinical point of view, there exists hence a very strong correlation between weekly increment in weight, HC and age, which is practical as these parameters are more easy to obtain than the length, even if that last parameter has very important value for appreciating « growth » (4,6,7). To illustrate the utility of the described formula, we may consider two examples. At 34 PCA weeks, 1 cm of gain in HC must be accompanied of a gain in BW of 358 g and vice versa ; at 28 PCA weeks, these numbers are 94 g BW, and 422 g BW at term . If PCA is not known, it can predict the PCA from the observed ratio[d BW / d HC ]. REFERENCES 1. Dancis J, O’Connell JR, Holt LE. 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APPENDIX 1: DOMBROWSKI, GAIRDNER ET BATTISTI CHARTS. - « Dombrowski » : PCA in weeks, BW in g, BL in cm and HC in cm; mean ( SD ) ; the original data can be found in reference 41 PCA weeks 25 26 28 30 32 34 36 38 40 42 - BL cm 31.6 ( 2.5 ) 33.1 ( 2.6 ) 36.1 ( 2.8 ) 39.1 ( 3 ) 42.1 ( 2.5 ) 44 ( 3.5 ) 45.9 ( 2.4 ) 47.7 ( 3.8 ) 49.5 ( 2.6 ) 51.3 ( 4 ) HC cm 22 ( 1.5 ) 23.1 ( 1.6 ) 25.3 ( 1.8 ) 27.4 ( 1.9 ) 29.5 ( 1.8 ) 30.9 ( (2.2 ) 32.2 ( 2.3 ) 33.2 ( 2.3 ) 34.3 ( 1.6 ) 35.4 ( 2.5 ) « Gairdner » : the original data can be found in reference 28: PCA weeks 25 26 30 34 38 42 46 50 54 60 - BW g 560 ( 90 ) 720 ( 115 ) 1040 ( 200 ) 1360 ( 218 ) 1685 ( 275) 2093 ( 335 ) 2500 ( 430 ) 2932 ( 469 ) 3365 ( 445 ) 3798 ( 608 ) BW g 800 ( 152 ) 900 ( 175 ) 1300 ( 245 ) 2500 ( 475 ) 2900 ( 550 ) 4300 ( 815 ) 4700 ( 890 ) 5100 ( 970 ) 5500 ( 1045 ) 5900 (1120 ) BL cm 35.6 ( 1.4 ) 36.5 ( 1.5 ) 40.3 ( 1.6 ) 44.1 ( 1.5 ) 47.9 ( 1.9 ) 51.7 ( 2 ) 55.5 ( 2.2 ) 59.3 ( 2.4 ) 63.1 ( 2.5 ) 66.9 ( 2.7 ) HC cm 26.2 ( 1 ) 26.7 ( 1 ) 28.7 ( 1.15 ) 30.6 ( 1.2 ) 32.5 ( 1.6 ) 34.6 ( 1.4 ) 36.7 ( 1.5 ) 38.8 ( 1.6 ) 40.9 ( 1.6 ) 42.8 ( 1.7 ) « Battisti » : the original data are given below and in references 10 and 11: PCA weeks 25 26 30 34 38 42 46 50 54 60 BW g 686 ( 89 ) 860 ( 112 ) 1555 ( 202 ) 2250 ( 293 ) 2950 ( 384 ) 3645 ( 474 ) 4340 ( 564 ) 5035 ( 654 ) 5730 ( 745 ) 6775 ( 880 ) BL cm 35.3 ( 2.5 ) 36.2 ( 2.5 ) 40 ( 2.8 ) 43.8 ( 3 ) 47.6 ( 3.3 ) 51.4 ( 3.6 ) 55.2 ( 3.9 ) 59 ( 4.1 ) 62.8 ( 4.4 ) 68.5 ( 4.8 ) HC cm 25 ( 1.5 ) 25.6 ( 1.5 ) 28 ( 1.7 ) 30.5 ( 1.8 ) 32.9 ( 1.97 ) 35.3 ( 2.1 ) 37.8 ( 2.25 ) 40.2 ( 2.4 ) 42.6 ( 2.55 ) 46.3 ( 2.78 ) APPENDIX 2: COMPLETE DATA CONCERNING « BATTISTI » ( 10,11 ) . Material: this is a local population that has been analysed between 25 and 60 weeks post conceptional age. Included infants had none malformations (221 were hence excluded), there was no abnormal genetic context, were singletons and had a normal obstetrical history of growth (863 had to be excluded). The measures were token at birth (n = 7650) and also on a longitudinal way till PCA (n = 4848). Population. PCA 25 –28 29 – 31 32- 35 36 – 39 40-42 43- 60 Total Measures at birth Measures afterwards 468 1252 1092 2494 2344 225 598 518 1190 1118 1199 4848 7650 Total 693 1850 1610 3684 3462 1199 12498 Statististical analysis of the normality of the population at birth : 1. PCA in weeks: mean = 36 (SD=4 ), median = 36.5, mode = 37.5 2. CV in % of weight : 13 ; of length : 7 ; of HC : 6 . multiple regressions: evolution of measured parameters of growth according to PCA: W in g = 174 PCA weeks – 3665, r = 0.99, SD = 13 % L in cm = 0.95 PCA + 11.53, r = 0.99, SD = 7 % HC in cm = 0.61 PCA + 9.72, r =0.0.98, SD = 6 % [ d W / d HC ] = 44 PCA – 1138, r =0.973, SD = 13 % [ d L / d HC cm ] per week = 0.094 PCA – 1.543, r = 0.88 , SD 14 % Figure 1. Reconstructed DOMBROWSKI chart: « PCA in weeks, BW in g, BL in cm, and Hc in cm 6000 Body weight 5000 4000 Body weight 3000 -2 DS +2 DS 2000 1000 0 25 26 28 30 32 34 36 38 40 42 PCa in weeks 70 Body length 60 50 Body length 40 -2 DS 30 +2 DS 20 10 0 25 26 28 30 32 34 36 38 40 42 PCA in weeks 45 Head circumference 40 35 30 Head circumference 25 -2 DS 20 +2 DS 15 10 5 0 25 26 28 30 32 34 36 38 40 42 PCA in weeks Figure 2. Reconstructed BATTISTI chart: « PCA in weeks, BW in g, BL in cm, and HC in cm 9000 8000 Body weight 7000 6000 Body weight 5000 -2 DS 4000 +2 DS 3000 2000 1000 0 25 26 30 34 38 42 46 50 54 60 PCA in weeks 90 80 Body length 70 60 Body length 50 -2 DS 40 +2 DS 30 20 10 0 25 26 30 34 38 42 46 50 54 60 PCA in weeks 60 Head circumference 50 Head circumference 40 -2 DS 30 +2 DS 20 10 0 25 26 30 34 38 42 46 50 54 60 PCA in weeks Figure 3. Reconstructed GAIRDNER chart: « PCA in weeks, BW in g, BL in cm, and HC in cm 9000 8000 Body weight 7000 6000 Body weight 5000 -2 DS 4000 +2 DS 3000 2000 1000 0 25 26 30 34 38 42 46 50 54 60 PCA in weeks 80 70 Body length 60 50 Body length 40 -2 DS 30 +2 DS 20 10 0 25 26 30 34 38 42 46 50 54 60 PCA in weeks 50 Head circumference 45 40 Head circumference 35 30 -2 DS 25 20 +2 DS 15 10 5 0 25 26 30 34 38 42 46 50 54 60 PCA in weeks